Hey! Sorry for the long response time, my internet's been really spotty and I haven't had the chance to check here! I would love some help for it to move to the areas I want if you're willing to help, I couldn't figure out how to do that- thanks!

UPDATE: Stormcrown is now objectively better than Clockwork, as explained in the guide

I forgot to mention Stormcrown, I'll be adding that in- thanks! As for whether or not it's worth it over clockwork, I would say no 9/10 times. 35 true damage to heroes is worthless at level 12, and Catherine is a fairly energy hungry character- so clockwork's greater energy regen and total bonus energy are more useful on her overall. Clockwork also allows for more frequent usage of Stormguard relative to Stormcrown, which is nice because it dramatically increases her survivability. 150 extra health from Stormcrown is nice, but not worth the reduced energy and cool down. The only time I can imagine Stormcrown being superior to Clockwork is if your carries suck at taking down objectives for some reason, and it is absolutely imperative that you capture some objective or the other.
Tl; dr: Clockwork>Stormcrown. Clockwork has better energy regen, bonus energy, and cool down- that utility far outweighs 150 extra health and the paltry bonus damage Stormcrown gives.
Thanks for asking- hope this helped!!
EDIT: Added in the Stormcrown Analysis

Lol- easily one of my favorite quotes of all time